Necessary for tests that depend on the state of the running context.
Since we support an SSE mode and an AVX mode, the FPR store truncate
test will fail on hosts that don't support AVX as the register offsets
are going to be different between the two. So we can conditionally
enable support for these tests.
Allows some something like the following:
"Env": {
"FEX_MAXINST": "500"
}
Not that I would recommend overriding MAXINST in the asm tests, as
command line overrides that